MurrayM
Guru
The Polynesians managed it.
Tides and Forward Progress
- Thread starter Nomad Willy
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The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
The Polynesians managed it.
RickB
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"You guys made way more sense arguing about anchors."
skipperdude
Guru
From reading all the thoughts on this question I have gained a bit of insight.
I started a thread on a similar issue on running the boat at a given rpm to maintain the true hull speed.
Without being able to run at slack tide with no current.
Without a true speed Thur water. As available with a pito tube mounted on the hull.
I have decided to maintain a given rpm and currents and tides be dammed.
I will get from point A to B and just enjoy the ride.
Hey MurryM. what is that photo of in your avatar and why did you select it for a boating forum?
I don't have any problem with it just curious.
SD
I started a thread on a similar issue on running the boat at a given rpm to maintain the true hull speed.
Without being able to run at slack tide with no current.
Without a true speed Thur water. As available with a pito tube mounted on the hull.
I have decided to maintain a given rpm and currents and tides be dammed.
I will get from point A to B and just enjoy the ride.
Hey MurryM. what is that photo of in your avatar and why did you select it for a boating forum?
I don't have any problem with it just curious.
SD
MurrayM
Guru
It's a piece of a beach on BC's north coast that I took while sea kayaking. We plan to use our 'new to us' vessel as a base camp, so we can explore even more such locations. The title and location is in my signature line.
Look for more in the future
SomeSailor
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My dog is a 160# Newfy, and although they are known for their seamanship I try to refrain from asking his advice.
I think Marin trusts his canine counsel more than he should at times.
How can there be any argument at all on this???
Carefully read my post # 54. Simple is as simple does!
1. Cruise with the current and faster "over-the-land speed" is realized, therefore using less fuel to travel a documented “land distance”.
2. Cruise against the current and slower "over-the-land speed" is realized, therefore using more fuel to travel a documented “land distance”.
As is depicted in my post # 54 there are some deep thinking (lol) processes required to make sure you consistently travel with the current... to help increase your “land speed” and therefore reduce your fuel usage. I’m sure every boater can figure those deep thinking processes out!
BTW, Marin (regarding your post # 55) my post # 54 does not pose theory – it states fact... just like this post!
Carefully read my post # 54. Simple is as simple does!
1. Cruise with the current and faster "over-the-land speed" is realized, therefore using less fuel to travel a documented “land distance”.
2. Cruise against the current and slower "over-the-land speed" is realized, therefore using more fuel to travel a documented “land distance”.
As is depicted in my post # 54 there are some deep thinking (lol) processes required to make sure you consistently travel with the current... to help increase your “land speed” and therefore reduce your fuel usage. I’m sure every boater can figure those deep thinking processes out!
BTW, Marin (regarding your post # 55) my post # 54 does not pose theory – it states fact... just like this post!
skipperdude
Guru
19Skipperdude Talk about your unique rock formations what is this.
0:25
WATCHED Freaky Fossilized human boot/ shoe print. Time travel?
4,357 views Found this fossil impression of what appears to be a set of tracks or boot prints in stone in a small cove in Prince William Sound Alaska.
Sorry I didn't mean to hyjack this tread.
I should have posted this on another place.
Is this considered a form of thread creep?
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OP
OP
Nomad Willy
Guru
skipperdude wrote;
"I have decided to maintain a given rpm and currents and tides be dammed.
I will get from point A to B and just enjoy the ride."
That's exactly what I do. But when something as interesting as this looms up ya just gotta think about it ... talk about it.
Not one of us would have thunk of all this stuff alone.
We can do lots of stuff here together that we can't do alone.
Rick your'e horney for anchors but you never had much or anything to say about anchors as I remember. I think there's more lurkers here than combatants.
Dogs ..... no I'm not going to go there.
"I have decided to maintain a given rpm and currents and tides be dammed.
I will get from point A to B and just enjoy the ride."
That's exactly what I do. But when something as interesting as this looms up ya just gotta think about it ... talk about it.
Not one of us would have thunk of all this stuff alone.
We can do lots of stuff here together that we can't do alone.
Rick your'e horney for anchors but you never had much or anything to say about anchors as I remember. I think there's more lurkers here than combatants.
Dogs ..... no I'm not going to go there.
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SomeSailor
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You need to update your chartplotter. Mine (Garmin) predicts the current flows and tides from the local stations and overlays those onto your display. It's handy to be able look ahead and realize you won't make it.
I also use sites like Dairiki to validate the predictions and then actual current reading from the local stations on my iPad/iPhone
RT Firefly
Enigma
Greetings,
Mr. SS. Newfoundlander would be the most polite term for your dog. I think Newfy is considered a derogatory term according to my sources but I guess the most PC term would be Newfoundlander and Labradorian.
Mr. SS. Newfoundlander would be the most polite term for your dog. I think Newfy is considered a derogatory term according to my sources but I guess the most PC term would be Newfoundlander and Labradorian.
skipperdude
Guru
Right on RT.
It is pronounced
New fund lander.
Not New found lunder
Not New found lund.
New fund land with the accent being on land not like New Englund
Not sure about the little pronouncement icons. sort of like
Illinois or New Orleans.
Some get irate if not pronounced as the locals
sd
It is pronounced
New fund lander.
Not New found lunder
Not New found lund.
New fund land with the accent being on land not like New Englund
Not sure about the little pronouncement icons. sort of like
Illinois or New Orleans.
Some get irate if not pronounced as the locals
sd
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And that is 1000% correct and end of discussion!!!
Moonstruck
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Two pilots don't make a right.
Now....I got one for y'all??? Does cross current affect your SOG at all??? On the circular slide rule, it says it does not. But I disagree.
That is only end of discussion if you do not plan correctly to exclusively travel with the current... read my posts #’s 54 and 67.
To travel against the current is unnecessary unless your schedule demands that you must travel against the current too, in order to meet time obligations. In that case I say you are on some fashion of a work party, rather than a pleasure party!
RT Firefly
Enigma
Greetings,
Mr. Baker. OK...Brain in gear...
Try to remember something about vectors...
Conclusion: Can't remember much but if the cross current is at 90 degrees, the only thing I think would have any effect would be a slight increase in drag due to the hull slewing sideways. Any angle other than 90 degrees to the beam will either add or subtract to SOG.
Good golly, thinking is tough!
Mr. Baker. OK...Brain in gear...
Try to remember something about vectors...
Conclusion: Can't remember much but if the cross current is at 90 degrees, the only thing I think would have any effect would be a slight increase in drag due to the hull slewing sideways. Any angle other than 90 degrees to the beam will either add or subtract to SOG.
Good golly, thinking is tough!
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MurrayM
Guru
When figuring out channel crossings while sea kayaking, we measured the distance of drift caused by current as if we paddled straight across on a compass bearing. The wider the channel, the greater the distance "off target" we would be taken by the current. This longer distance was what we used to estimate how long it would take, because to get to our intended destination we would have to angle into the current an equal and opposite angle to the angle of drift, to counteract drift. This meant a much longer crossing time than if we could simply paddled straight across. So, in this case, SOG is definitely affected.
Now....I got one for y'all??? Does cross current affect your SOG at all??? On the circular slide rule, it says it does not. But I disagree.
Exact 90 degree (any degree less or more will also somewhat alter SOG results) cross current affects "straight line" SOG (point A to point B) in that you must tack an extent (length and duration of tack depends on cross current speed) to stay on course to reach point B from point A. This means you traveled a somewhat (a little bit) further in total "over land" distance. Therefore the comparison of SOG calculated if traveling on a straight line from A to B would be faster than equivalent "straight line" SOG from point A to B when tacking due to cross current. All comparisons are figuring no wind whatsoever.
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Now....I got one for y'all??? Does cross current affect your SOG at all??? On the circular slide rule, it says it does not. But I disagree.
Whoooaaa! Now you're getting into a deep vector analysis with longitudinal and lateral components of speed vs. cross current. I questioned this in college after using the CR-3 and ran the numbers when my math skills (and some will argue thinking capacity) were honed like a razor sharp knife. The results were that the speed drop was so small as to be negligible. Surprised the heck out of me. That's not to say that the slower boat speeds and higher relative current speed wouldn't have a greater impact on your forward speed vector component. I'm not going to calculate it, though! ;-)
"Two pilots don't make a right."
Moonstruck, two wrongs don't make it right, but two wrights make it right!!
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RT Firefly
Enigma
Greetings,
Mr. FW. Shouldn't that be two Wrights make a pilot?
Mr. FW. Shouldn't that be two Wrights make a pilot?
RT - Good One Liner! You're starting to sound more and more like the fine fellow on your avatar!!
RT Firefly
Enigma
Greetings,
Mr. Art. I RESEMBLE THAT REMARK!!!!!
Mr. Art. I RESEMBLE THAT REMARK!!!!!
xfedex
Senior Member
BTW, Marin (regarding your post # 55) my post # 54 does not pose theory – it states fact... just like this post!
Your SOG faster with the current, SOG slower against the current is indeed a fact. My dog instinctively knows this, too, as he has to put it into practice every time he retrieves something from the water and comes back in a cross-current.
My comment was on the notion (theory) of accurately calculating the current effects for a voyage up or down the Inside Passage. The data necessary for accurately doing this simply doesn't exist along much of that route. So all one has to work with are general current averages. That inaccuracy combined with the extremely variable local currents along the way in the maze of channels and passes one goes through make it pretty impossible to come up with a truly accurate prediction of time and fuel consumption.
In other locations--- SFO Bay perhaps--- where the current data is complete and the geography does not have the same extremely varied effect on local currents over such a huge distance, it is much easier to accurately predict time and fuel use for a cruise.
That's my only point.
OP
OP
Nomad Willy
Guru
Get a grip Marin your dog dosn't know s##t.
And John I though the end of this discussion was about 8 posts ago. Walt used to say that ... "end of discussion" when he'd get frustrated. Had about the same effect then as now. I don't see the discussion ending until the posts stop and unlike the tide that's not very predictable.
And John I though the end of this discussion was about 8 posts ago. Walt used to say that ... "end of discussion" when he'd get frustrated. Had about the same effect then as now. I don't see the discussion ending until the posts stop and unlike the tide that's not very predictable.
You need to update your chartplotter. Mine (Garmin) predicts the current flows and tides from the local stations and overlays those onto your display. It's handy to be able look ahead and realize you won't make it.
We've had that technology on the boat for years now on the Furuno and we also have it on the iPad and the Standard Horizon plotter on the Arima. Even all the lighted navaids flash with the actual sequence that's on the real navaid. Nice feature but it doesn't give you all the data you need to accurately calculate a trip up or down the Passage. In fact it doesn't give you the all the data you need to accurately calculate a trip through the San Juan and Gulf Islands. It gives currents in the more important passes and the average current for larger bodies of water like the Strait of Georgia, Haro Strait, etc.
But it doesn't give you any of the current variations across these bodies of water, just the mainstream average. It's not going to tell me what the south side current strength is in Mosquito Pass at such and such a time, for example, or what the difference is between the ebb current speed in the middle of Spieden Channel and the ebb current speed over against the San Juan Island shore of the channel. These speed differences can be pretty significant at times and have a significant effect on your SOG and the time it take to get somewhere. But there's no way to calculate this in advance because there are no numbers to do it with.
The only way to take advantage of those differences is local knowledge. We've learned over the years what side of the passes and channels to favor at what stages of the current flow in the passes and channels we use a lot. But there is no way to figure this out beforehand because there are no numbers to use.
And go halfway up the Passage and try to find accurate data for a route you may be following up some channel. It's often simply not there because the data for many of the channels up there has never been taken or if it has been it's not published anywhere you can use it..
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SomeSailor
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Actually no... He's a Newfoundland dog. We owners call them 'Newfys' or 'Newfs'
That's unfortunate... He's doesn't seem to mind. That's all that really matters to me.
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